Tonearm Effective Mass
Tonearm effective mass expresses the arm’s inertia—its resistance to changes in motion—as felt at the stylus. It is given as an equivalent mass in grams.
This differs from the arm’s physical weight. Its mass distribution matters: a part near the pivot contributes differently from the same mass farther away.
Tonearm Effective Mass — Tonearm
Match the arm to cartridge compliance: how flexible the stylus suspension is. The combined effective mass of the arm, headshell, cartridge and mounting screws, together with compliance, determines resonance, a frequency at which vibration is amplified. With compliance unchanged, increasing this total lowers that frequency. A more flexible suspension generally calls for lower effective mass. Lower mass is not automatically better.
Check whether the quoted figure includes the headshell (cartridge holder), cartridge or mounting screws before combining masses; count each only once. The cartridge weight range the counterweight can balance is a separate limit, not the arm’s effective mass.
Tonearm Effective Mass — Turntable
On a complete turntable, this figure belongs to the fitted tonearm, not the deck or platter. Use the specifications for the arm actually installed, especially after an arm replacement.
Before changing the cartridge, check its mass and compliance against that arm, then check the counterweight’s supported cartridge weight range separately. A cartridge can balance yet be a poor resonance match. If the published effective mass does not say which parts it includes, check the manufacturer’s documentation or ask before calculating.
Sources
- Tonearm cartridge resonance — Kuzma
- TA-110 9 inch — Ortofon
- Find the right cartridge — Ortofon
- Phono Cartridges: cartridge-making dictionary — Audio-Technica
- Debut PRO B — Pro-Ject
- Tonearms FAQ — Kuzma